Internal combustion engine



Dec, 16, 1941. H. A. RoAN 2,256,077

' ITERNAL COMBUSTION ENGINE Filed Oct. 5, 1938 lO Sheets-Sheet l ff/@Hwy A. H0017 Dec. 16, 1941. H. A. RoAN INTERNAL COMBUSTION ENGINE Filed Oct. 3, 1958 l0 Sheets-Sheet 2 `HIGH SPEED LOW SPEED j/Yzjg. Q

STANDARD ws wm Hp no EXHAUST CLOSES' OPENS INTAKE CLOSES EXHAUST cLosEs 0 4 8 EXHAUST OPENS r/ T IM I'NG 2 NTAKE OPENS .ms AE T S mw C EXHAUST CLOSES EXHAUST OPENS TIMING #29 INTAKE OPENS 2/ L o nNTAKE 2 5"23 CLOSES Dea.A 16, 1941. 7 H. A. ROAN 2,266,077

l INTERNAL COMBUSTION ENGINE Filed oct. s, 1958 1o sheets-sheet s v jlzgj 712119.15

Henry A. 10017 awww l Dec. 16, 194:1. H. A. RoAN 2,256,077

INTERNAL coMBusTloNNGINn Filed oct. 3, 1938 10 Sheets-sheet 6 Wig. 2Q

` Jaan Dec; 16, 1941. H. A` ROAN r 2,266,077

INTERNAL COMBUSTION ENGINE I Filed oct. s, 1958 1o sheets-sheet? lNTAK E LOW SPEED gmd/ 5 17617139 A. F6019 Dec. 16, 1941. H, A ROAN 2,266,077

INTERNAL coMUsTloN ENGINE Filed oct. '3, 1938 1o sheets-sheet B EXHAUST L ow SPEED De. `1s, 1941. H A, RQAN 2,266,077

INTERNAL COMBUSTION ENGINE Filed 0G12 3, 1.958 l0 SlleebS-Sheel'I 10 @9.35 171237. 39 H1719. 40 LOW SPEED STANDARD HIGH SPEED Exrmus rxr-Au cs osEs cs os 0 Hb 28 mTAKx-:S y. j

CPEN /b ExHAusr y. cLo sssomg'smE 'F'EQJSE- :W4 INTAKE beglf i cLosEs NTAKE o :Loses 25 42 v .62

*u* Uuly NV WTAT/ cLosEs trate the invention,

parts throughout the several views.

Patented Dec. 1e, 1941 i iN'rE'nNAL cormusrloN ENGrNE Henry A. Roan, Minnealwls, Minn Application october a, 193s, serial Nu. 233,103 zzolauns. (ol. 12ssm This invention relatos to mechanism for varying the timed action of valves of internal combustion engines, and has as an important object to increase the eiiiciency of internal combustion wherein engines, particularb engines ofthe' type valves are operated by cams, and to this end, `I provide a highly eicient and relatively simple mechanism whereby the timed action of the valves may be so regulated that the engine will operate at maximum etliciency through its entire range of speeds.

The above and other important objects and advantages of the invention will be made apparf ent from the specification and claims.

In the accompanying drawings-which illuslike characters indicate like Referring to the drawings:

Fig. l is a transverse vertical section through a cylinder and the axis of the co-operating exhaust port and valve of an engine incorporating a preferred embodiment of the invention;

Fig. 2 is a transverse vertical sectional view similar to Fig; 1, and taken through-the same cylinder as Fig. 1, but differs from Fig. 1 mainly in that it is taken through the axis of the intake port and valve o the cylinder instead of the exhaust port and valve as in Fig. 1;

t Figs. 3, 4 and 5 are valve-timing diagrams il-l lustrating various diierent valve timings obtainable in engines incorporating the invention;

Fig. 6 is a fragmentary transverse sectional view taken on the line B-'S of Fig. 7;

Fig. 7 is a fragmentary horizontal sectional view taken on the line 'l-l of Fig. 6;

Fig. 8 is a detail sectional view taken on the line 8-8 of Fig. 6;

Fig. 9 is an enlarged fragmentary detail view of certain important parts of the preferred form of variable timing exhaust valve operating mechanism incorporated in-Fig. 1;

Fig. 10 is a View similar to Fig. 9 but illustrating corresponding parts of the preferred form of variable timing intake nism incorporated in Fig. 2;v

Fig. 11 is a fragmentary right toward left in respect to Fig. 9 or from left to. right in respect to Fig. 10, some parts being broken away or omitted and some parts being shown in section;

Fig. 12 is a view similar to Fig. 9 but illustrating a somewhat modied form of exhaust valve operating mechanism;

Fig. 13 is a fragmentary view looking from right toward the left in respect to Fig. 12;

valve operating m echa view looking from l Fig. 14 is a fragmentary sectional view taken 0n the line M--ll of Fig. 12;

Y i .-15, 16 and 17 are views in side elevation` 'o'f'each of the several parts of the' multiple section tappet structure shown in Figs. 12, 13 and 14.

Fig. 18 is a view looking from right to left in respect to Fig. 16; f'

Fig. 19 is a View respect to Fig. 17; v Fig. 20 is a horizontal sectional view taken on 100mg from right to left in the une zs--zs of Fig. 1o;

Fig. 21 is a diagrammatic view illustrating .certain slight variations in application, particularly of the form of the invention illustrated in Fig-s. 1 to 11 inclusive and 20;

Fig. 22 is a substantially full scale vfragmentary sectional view of an internal combustion engine incorporating still another form'of the invention, the section in this instance being taken through the axis of the engines intake valve;

Fig. 23..is a detail view corresponding td Fig. 22 but with some parts omitted and some additional parts broken away and shown in section;

Fig. 24 is a view showing a diierent position of the parts shown in Fig. 23;

Figs. 25 and 26 are views similar to Figs..23 and 24 but illustrating the exhaust valve operating mechanism -of the engine o Fig. which may b'e assumed to be directly behind the intake valve mechanism of Fig. 22;

Fig. 27 is a detail sectional view parts omitted and some parts broken shown in section taken on the line Fie. 22; y

Fig. 28 is a detail perspective view with some parts broken away and some parts in section of the parts of the tappet mechanism of Fig. 27;

Fig. 29 is a Adetail sectional view taken on the line 29-29 of Fig. 28;

with some away and 21-21 of Fig. 30 is a detail sectional view taken on the line f30-30 oi Fig. 28;

Figs. non-shiftable tappet element of Figs. 22 to 30 inclusive. Y

Fig. 33 is a perspective View of one of the shiItable tappet elements of Figs. 22 to 30 inclusive.

5.5 parts in axial section;

22, and

31 and 32 are-perspective views of the i Fig. 36 is a sectional view through the crank shaft to the engine of Fig. 22 and partially illustrating the lay-out of the intake and exhaust cams and the relative positions of the intake and exhaust valve operating cams on the crank shaft for the purpose of obtaining the particular valve timing herein disclosed;

Fig. 37 is a sectional view through the variable timing mechanism control shaft and illustrates the relative positions thereon of the operating\10 eccentrics of the intake and exhaust valve mechanisms;

Figs. 38. 39 and 40 are valve timing'diagrams illustrating several diil'erent valve timings obtainable by means of the mechanism disclosed in Figs. 22 to 37, inclusive; and

Fig. 22a is a sectional view substantiallyvcorresponding to Fig. 22, but being sectional through the axis of the exhaust valve of the cam cylinder of the engine as in Fig. 22.

With reference first to the conventional parts of the engine, shown in Figs. `l and 2, the engine block, indicated as an entirety by the numeral 28, is formed -with the desired number of cylinders 21 and about the cylinder or cylinders with 'waterf jackets 28. The engine block 28 is also formed to afford the upper portion of a crank case 29 that is normally closed and completed by means of a removable base 80. Since only one cylinder of the engine and its co-operating parts are herein illustrated, only one cylinder and its co-operating parts will hereinafter be referred to. although it should be understood that the invention, by mere duplication of certain parts, adapts ,itself to engines having any number of cylinders.

The cylinder 21 is normally closed in the conventional manner by a water-jacketed cylinder head 3|- that is formed to afford a combustion chamber 32 and is provided with the usual spark plug 93. Working in the cylinder 21 is a piston 84 that is connected by lmeans of a wrist pin 85 and connecting rod 98 to the throw or crank 31 of a crank-shaft 98.'

Formed in the engine block 28 for communication with the cylinder 21 are intake and exhaust ports 89 and 4I, respectively. These ports' 39 and 4| are respectively controlled by conventional type poppet valves' 49 and 42.A 'I'he axial stems .l 43 of these valves 48 and 42 work and are guided for true vertical reciprocating movements in guides 44. In accordance with usual practice the valves 40 and 42 are maintained under yielding closing pressure by means of coiled compression springs 45 applied around their stems 48, which stems, at their lower end, are provided with the customary adjustable tappet-engaging nuts 45.

Mounted in suitable bearings in and extending longitudinally of the crank case 29 is a cam shaft 41 that is provided with a cam 48 for the intake valve 40 and a cam 49 for the exhaust valve 42.

` The cam shaft 41` is, asv-usual, driven from and in a predetermined timed relation to the piston through connections including the piston driven' crank-shaft 38, a timing gear 89a on one end of the crank-shaft, timing gear 88h on the same end of the cam shaft, and a chain 98e running. over said gears.

' It is, of course, necessary in order that .the valves 40 and 42 will be operated from their cooperating cams 48 and 49, respectively, to provide suitable, operating'connection between the cams andthe stems of their respective co-operating valves and in accordance with the several examples of the invention herein illustrated, as well as in general practice, such operating connections between the cams and valve stems are afforded by means of floating members known in the art as tappets. The tappets herein illustrated, however, Vare novel in character, having cam-engaging surfaces that are so adjustable in respect to the cams as to effect desired variations in the action of the valves. The term tappet is herein used in a broad sense and is intended to include any member operated dircctlyby a cam and. serving as an operating link between the-'cam and valve whether it constitutes the sole link or one of several connecting links. v l With reference now to the embodiment of the invention illustrated in Figs. 1, 2, 9, 10 and 11, the intake valve operating tappet, see Figs. 2, 10 and ll, is indicated as an entirety by 5l and the exhaust valve operating tappet, seeFigs. 1, 9 and 11, is indicated as an entirety by 5I. In the particular engine illustrated, which is of the socalled L-head type. the tappets 50 and 5l serve as the onlyconnecting links between their respective co-operating cams and valve stems, this being conventional practice in L-head engines.

The tappets 50 and `5I are alike but in use are turned 180, one in respect tothe other. Each of these tappets comprises 'a stem-like valveengaging main body 52, formed at its lower end 1 in and extends through segmental slots't! in opposite sides of the flanges 54. The curvature of the segmental slots 82 conforms to that of a circle struck from the'axis of the cam shaft 41 and the Journal pins are shiftable therein from extreme positions wherein they and their rollers 59 are co-axially aligned'with the non-shiftable rollers 58 and their pivot pins 88 to opposite extreme positions considerably removed' from the rst-noted extreme positions, in the direction of rotation of the cam shaft in the case of the intake valve-operating tappet 5U, and in a direction opposite to the direction of rotation of the cam shaft in the case of the exhaust valve operating 'tappet 5i. The stem-like bodies 52 -of the tappets 50 and 5| engage the stems 42 of their respective co-operating valves 40 and 42 ,and work freely in guide bearings 55 in the engine block. The rollers 59 and 59, of course, ridealtemately on the cam shaft 41 and their co-operating cam 48 or 49, the valves being opened under engaging movements of their co-operating cams with their co-operating tappet rollers and being closed by valve springs 45 under disengaging movements of the cams from the tappet rollers.

It will, of course, be evident that when the tappet rollers 59 are aligned with their respective co-operating rollers 58, the tappets will function exactly as do conventional types of roller tappets since the cams will engage and disengage both their respective co-operating rollers simultaneously; and it will further be evident that when the rollers 58 are shifted the duration of the open periods of the valves will be increased,

Y tappets to. provide asomo?? `mounted on the cam shaft adjacent the bearing a set-screw or the like 13. One,

It is customary in engines employing roller co-operating cams with relativelyblunt or broad noses as compared to cams used in connection with flat faced tappets, so as to slow down the reversing action of the valves.

This same practice is preferably followed in connection with the roller tappet embodiment of the invention illustrated in Figs. l, 2, 9, 10 and 1l, for the reason given above when the rollers 89 and 59 are aligned, and for the further reason that when the co-operating rollers 58 and 59 are shifted, one in respect to the other, the nose of the co-operating cam 48or 49 position of dead center on one of said rollers to a position of dead center on the other thereof without producing or permitting appreciable movement of the tappet or itsv co-operating valve. Since in the tappet structure described there are two cam-engaging elements, to wit: the rollers 58 and 59, the tappets may be properly termed multiple section tappets" to distinguish the same from conventional tappets having one camengaging element or surface.

As a simple and effective means for simultaneously shifting the rollers 59 of tappets 59 and in opposite directions, I provide operating mechanism including an operating shaft 96 having formed or rigidly secured thereon eccentrics 65 and 65a which eccentrics, it will be noted, while alike, are rotatively positioned 180 apart on the shaft 66. The eccentric B5 is connected to operate the roller 59 ofthe exhaust valve tappet 5| by means of an eccentric strap 94 and a rigidly attached yoke 63 opposite free end portions of which yoke receive opposite projected ends of journal pins B0. connected to shiftable roller 59 of tappet 50 by means of a like eccentric strap 64a and yoke 88a. The opposite arms of'yokes 63 and 93a are securely but removably applied to the straps 94 and 64a, respectively, by screw-threaded bolts or the like 61. The-shaft 6B extends in parallel relation to the cam shaft 41 and is suitably journaled at its ends in the end portions of the crank case.

The shaft 66 may, of course, be operated in a number of ways, either manually or automatically, but is preferably automatically operated according to engine speed in such a manner that vthe timing of the intake and exhaust valves 40 and 42, respectively, will be so varied, according to the speed of the engine, that the engine will, at all times, regardless of speed be operated at a point of maximum eiciency. This automatic regulation of the valve timing is most conveniently accomplished by means of a centrifugalgovernor such, for example, as the governor illustrated in Figs. 6 to 8, inclusive. y

Before describing the governor, attention is called to the fact that the cam shaft 41, besides being journaled at its opposite ends in the crank case as previously stated, is also intermediately journaled in a bearing supported from the crank case. The governor, in the form herein illustrated, includes a pair of centrifugally actuated arms 69 that are each intermediately-pivoted at 10 in the bifurcated end 1i of a fixed collar or bearings B8 which are 12 that is securely.

will move from a csa-operating parts The eccentric 95a is similarly 4l. by means of end of each of the intermediately pivoted arms 49 is enlarged to provide aweighted portion 14.

Axially slidably mounted .on the cam shaft 41 is a shifter collar 15 having diametrically opposed cam surfaces 16, each of which isv normally engaged by the light free end of a different centrifugally actuated arm or lever 99. The shifter co1lar'1whiie axially shiftable in respect to the fixed collar 12, is caused to rotatel in common therewith by means of asliding pin engagement at 11. trifugal action the mediately pivoted weighted ends 14 of the inter'- thereof will press against the the shifter collar and cause the shifter collar to `move extreme position shown by To transmit the movement of the shaft 99, that is pivoted to the crank case at 19. The free end of one arm of this bell-crank 18 is moved by the shifter collar 19 through the medium of an anti-friction bearing 80 with which it has condotted lines in Fig. 8.

stent engagement and the free end of the otherA arm of the bell-crank 18 works in the bifurcated end of a lug 9| which projects from the shaft' 68. The parts 15, 18, 9| and 69 and other parts controlled thereby, are at all times retained under tension to move to theirnormal positions, shown in full lines, by a coiled tension spring or the like 82, the tension of which may be adjustably varied by means of a suitable tension-adjusting bolt or the like 83. The coil spring 92 maintains `its in their full line positions when the engine is idle or running at very low speeds, but as the speed of the engine is progressively increased the weighted ends 14 of levers 99 are moved progressively outward under increased centrifugal action, the yielding action of the spring @2 will be increasingly overcome and the shaft 88 will be moved in a clockwise direction.

This clockwise rotation of the shaft 89, under I increased engine speed, produces shifting o f the tappet rollers 59 in opposite directions from their normal positions tive co-operating rollers 59; this shifting, due to the-settings of the eccentrics and 95a, vbeing in the direction of rotation of the cam shaft 41 in the case of the intake valve tappet 50 and being in a counter-cam shaft rotation direction in the case of the exhaust valve operating tappet 8l.

' Certain of the valve timings obtainable with the preferred arrangement described are indicated diagrammatically in Figs. 3, 4 and 5. In these figures the circles marked a indicate4 one complete rotation or 360'.' crank 31, and hence, one complete reciprocation or two strokes of the piston 34; the vertical lines marked b indicate top dead center position of the crank 31; vertical lines marked c indicate bottom dead center position of the crank 31; and the arrows d indicate the direction of rotation of the crank 31.

operation of Figs. 1 to 11, inc. l During the starting period and when the engine is running at very low speed, the shaft 66 will be maintained, by the governor spring 82, in its extreme counter-clockwise position and the shiftable rollers $9 will be in positions of alignment It will now be obvious that under cenlevers 69 will move outwardly" and the inner ends `caxn surfaces 1S of toward the left to an this collar 15 to y there isprovided 'a bell-crank 18 of alignment with their respecof movement of the all intake and-exhaust periods, with respect to thel position and travel of the piston 34 and crank 31,

will be substantially as follows: a.

The cam 49 will come into simultaneous engagement .with the rollers 58 yand 59 of tappet 5| and begin to lift said tappet and open the exhaust valve42 whenY the piston-operated crank 81 comes to a position 23 before bottom dead center of the downward working stroke of the piston; as shown by full lines in Fig. 1 and Fig. 9

and indicated diagrammatically by a line e in Fig. 3.

The exhaust valve will now be held open more or less during the balance of the downward working stroke of the piston and during the entire upward exhaust stroke of the piston and will finally be closed and terminate the exhaust period when the piston crank is 2 past top center, as indicated diagrammatically by line j in Fig. 3. When the piston crank 31 is in a position 2 in advance to its position at the time of complete closing of the exhaust valve 42 or at top dead center at .the tennination of the exhaust strokeof the piston, the cam 48 comes into simultaneous engagement with rollers 58 and 59 of tappet 58 and begins to raise and open said tappet and the intake valve 48 to start the intake period, such point of opening of the intake valve for low speed operation being indicated diagrammatically byline b in Fig. 3. The intake valve will now be held open more or less during the entire downward' intake stroke of the piston and during the initial upward cornpression stroke, complete closing of the intake valve being effected when the piston crank 31 is 25past bottom center on its upward compression stroke, as illustrated by full lines in Fig. 2 and indicated diagrammatically by line g in Fig. 3. Otherwise stated, the vexhaust valve will, under low speed operation, be open more @or less during 205 of movement of the crank. .31 and the intake valve 48 will be open during 205 of movement of the crank 31..

It is important here to bear in mind that the above described low speed timing is obtainable with the `co-operating rollers 58 and 59 of tappets 58 and 5| in co-axial alignment, in which I positions the tappets 58 and 5| act as conventional roller type tappets, since both co-operating rollers of each tappet are simultaneously engagedand disengaged by their co-operating cams 48 or 49. .Y

As the speed of the engine is progressively increased the rollers 59 of tappets 50 and 5| will be progressively shifted from positions of axial alignment with their respective co-operating rollers 58, the former in the direction of rotation of the cam-shaft and the latter in a counter camshaft rotation direction, until at very high speed the rollers 59 will be shifted to their extreme high kspeed positions, shown by dotted lines in Figs. 1, 2, 9 and 10. With the tappet rollers 59 in this position for high speed operation, the timing of the intake and exhaust periods will be substantially as diagrammatically indicated in Fig. 5, wherein the line e indicates the time of opening of the exhaust valve and the beginning of the exhaust period as being when the piston crank 81 is 68 before bottom center; the line ,f

indicates the closing of the exhaust valve as being when the piston crank is 2 past top center: and g indicates the closing of the intake However, it may be stated ythat for high speed operation the opening of the exhaust valve has been advanced 45 in respect to the travel of the piston crank 91 and the closing of the intake valve 48 has been retarded 45 in respect to the travel of the piston crank without, however, affecting the time of closing of the exhaust valve or the time of opening of the intake valve. In other words, for high speed operation the duration of the open periods of the exhaust and intake valves has been increased, in respect to the travel of the piston crank, by 45 of movement of said crank irrespective of and without affecting the time of closing of the exhaust valve or the .time of opening of the intake valve.

' Fig. 4 diagrammatically represents an obtainable intermediate speed timing and in this figure, line e indicates the opening of the exhaust valve 48 before crank bottom center; f indicates the closing of the exhaust vvalve 2 past crank top center; b indicates the opening of the intake valve at crank top center; and g indicates closing of the intake valve 50 past crank bottom center.

The valve timing diagrams of Figs. 3, 4 and 5 are merely indicative of possible timings obtainable by means of the invention and since the merits of variable valve timing appear to be generally recognized, no detail description of the advantages thereof is thought necessary.

that whereas relatively long compression and power strokes are desirable for starting and for low speed operation and will result in. materially higher eiiiciency and smoother performance at low speeds, relatively long intake and exhaust periods become of increasing importance under increased engine speed.

These requirements are obviously fully met with the mechanism described and engines employing the same may be made to operate ator near maximum efficiency throughout their full speed range, whereas, engines employing fixed timing must essentially be highly efficient over a relatively narrow range of speeds. It will of course be appreciated that substantially any engine designed to employ roller tappets may readily be arranged to accommodate the multiple section roller tappet mechanism described by merely enlarging the crank case sufficiently to accommodate the eccentric shaft 86. However, in some engines, designed primarily for use of mushroom type tappets, there may not be sufficient clearance between the cam and tappet guide bearings to accommodate my roller tappet arrangement, and, therefore, for use in such engines and for use by designers who prefer to use mushroom type tappets, I provide the multiple section tappet arrangement illustrated in Figs. 12 to 19 inclusive.

Description of Figs. 12 to 19 In this form of the invention, as in the first form described, the exhaust valve and intake valve operating tappets are structurally alike and are merely applied in positions rotated one in respect to the other, sothat the shiftable elements thereof will be shiftable in opposite directions. In view of this fact only the exhaust valve operating tappet is illustrated, being indicated as operation the shaft 68' 4tappet will y y acciao?? This latter form of tappet relatively sharp -nosed cams of the character more generally used in connection with mushroom tappets. Such a cam shaft is indicated in Figs. 12 and 13 by 41' and the -relatively sharp nosed exhaust valve operating cam thereof is indicated by 48'.

The multiple section mushroom typetappet comprises a vertically disposed stem 52' formed rigid1y"w'lth the horizontally disposed fixed or non-shiftable cam-engaging section 58', an adjustably' supported shiftable cam-engaging section 58', and an intermediate oating cam-engaging section 84. The upper surface of .the shiftable section 58' is arcuate in the plane of movement of cam 49'. works against a similarly formed surface on the under side of the stem 52', and is provided, at its outer edge, with an inturned flange 85 affording -an arcuate channel to receive and work slidably -over an arcuate flange 85' on the stem 52'. For retaining the parts together the shiftable section 59' is provided with a laterally projecting pin 86 that works through a segmental or arcuate slot 81'in the fixed tappet section 58'. The segmental slot 81 and the several arcuate surfaces above noted are struck from the axis of the cam shaft. The floating section 84 is interposed between sections 58' and 59' and over the pin 86 which latter, said section 84, is slotted at 88 to receive pin 8G. The slot 88 is shorter than slot 81 so that the floating member 84 will partake of only approximatelyone-half the movement of section 59'.

Shiftable section 59' is provided in axial aligny ment with its pin 88 with a short pin 89.

The operating mechanism employed in connection with this last noted form of tappet is equivalent to that used in connection with the roller type tappet, the eccentric shaft being in dicated by 66', the exhaust valve'tappet operating eccentric thereof by 65', the eccentric by 84', and the yoke by 83'.

The opposite ends of the yoke 83' are provided with suitable apertures to receive the ends of pins 86 and 89 and when applied the yoke 63 serves toV hold the tappet parts against axial separation. The eccentric shaft 68' may be assumed to be provided with a suitable governor such as shown in connection with shaft 68 whereby under starting conditions and low speed progressively increased engine speed will be profgressively rotated in a clockwise direction. Under these conditions the variable timing Vobtainable will be exactly the same as that provided by means of the roller tappet arrangement and diagrammatically indicated in Figs. 3, 4 and 5. Under low speed operation the cam-engaging surfaces of sections 58', 58' and 84 of tappet 5|', will be aligned and engaged anddisengaged simultaneously by the cam and the action of the be exactly like that of conventional mushroom t e tappet and also like that of roller tappet 5| when both of itsv rollers 58 and 58 are aligned. The low speed timing obtained with the parts thus aligned is as indicated in Fig. 3. Under high engine speeds will be moved to an ex-L- treme counter-clockwise position and under to the other',

the sections 58 and 84 15 tions |22 'and |23 are of tappet 5| be shifted in a counter cam shaft rotation direction to the maximum extent permitted by slots 81 and and sections 59', 84 and 58' will be successively engaged, thereby advancing the time of opening of the exhaust valve a .obviously the valve action will be smoother when said section is incorporated. It will also be obvious that if the intake and exhaust valves are each provided with a tappet, like rotatively positioned apart,

tappet 5|', but

the timing of the intake and exwill be as indicated in Figs. 3, 4

haust valves and 5.

nesr'ipiionpf Figs. z2 io 4o. inclusive The engine illustrated in Figs. 22 and 22a is like the engine of Figs. 1 and 2 except .for slight modifications. made for the purpose of accommodating the modified f'orm of the valve actuated timing mechanism of Figs. 22 to 40 inclusive. Of the conventional parts of this engine herein illustrated, the engine block is indicated as an entirety by the numeral |88. VThis block is formed with the usual cylindrical bore |8| and about the cylinder |8| with water jackets |82. The upperportion of the crank case of the engine, cylinder block, is indicated by |83. This crank case forming portion of the block is formed to enclose the variable timing valve actuating mechanism. The upper end of the cylinder |8| is closed by a water jacketed cylinder head |84 that is formed to afford a combustion chamber |85, and which is provided with the usual spark plug |86. Formed in the engine block |88 for -valve guides H2. These valves are maintained to-close against their seats ||3 by means of the usual coil compression l under yielding tension springs H4.' The valve springs vand associated mechanism are contained within a valve mechanism compartment ||5 above the crank case 'and laterally oli-set from the cylinder, and

which compartment is normally closed by a removable cover plate ||8. The cam shaft of Figs. 22 and 22a is indicated' by numeral ||1. This cam shaft may be assumed to be journaled within the crank case in the conventional manner:

and t0 be driven in the conventional manner from the engines crank case, not shown.

The cam shaft ||1 is provided with intake and exhaust valve operating cams individually indicated as entireties by numerals ||8 and ||9 respectively. These cams. which are peculiar in character, operate the intake and exhaust valves |88 and ||8 respectively through the medium of the novel tappet mechanisms |28 and |2|.

The cams ||8 and ||9 are alike but are reversibly .applied side for side on the cam shaft and each comprises main and supplemental sections |22 and |28 respectively that are laterally and circumferentially oi-set one in respect to the other. These main and supplemental cam secintegrally formed' and one in respect and which is formed integrally with the ing being, of course.

faces of the supplemental cam sections are circumferentially spaced l" from the corresponding lifting surfaces of the main cam'sections. This is clearly illustrated in Fig. 36 wherein it is also shown that the intake and exhaust valve operating cams ||2 and ||0 respectively are alike b ut reversibly applied on the cam shaft ||1.

By reference to Fig. 3,6' it will be also seen that the main section of the exhaust valve operating cam H2 is rotatively advanced on the cam shait'-1l1.5 with respect to the main section of the intake valve operating cam ||2 in the direcv tion of rotation of the crank shaft which is clockwise -in respect tothe drawings,`such spacreclted solely for the purpose of obtaining the particular variable valve timingrange herein recited for the purpose of illustrating a preferred embodiment of this form of the invention. Obviously from the drawings, it

" will be seen that the adjoining lifting surfaces of the main and supplemental c am sections are tangential.

'I'he tappet structures |20 and |2|, which constitute the connecting links between the cams ||5 and ||2 respectively and the stems of the intake and exhaust valves |09 and ||0 respectively, each include a stem-like valve engaging main body |24 that is rigidly formed at its lower end with a supplemental cam section engaging head |25," and at its upper end is provided with valve clearance adjusting nuts' |22. The tappet stem-like body |24 is slidably mounted in Aand guided for true straight line reciprocating movements by a bearing sleeve |21, the axis of which is preferably'and is herein illustrated as being radial of the cam axis (see 1 particularly Fig. 35). In accordance with the present illustration the bearing sleeves |21 are provided with mounted flanges |22, through the medium of which and bolts or the like |29, the bearing sleeves' are detachably anchored to the engine Iblock casting. The rigid heads |25 of the tappet stems'are formed to afford relatively obliquely disposed-supplemental cam section engaging surfaces |22 and |2|. In the forms of the invention illustrated, the cam engaging surfaces |20 and |2I are straight and are disposed at obtuse anglesI one in respect to the other, and the Junction of these surfaces describe or have as their locuses, straight lines that extend uni-dithe tappet heads |25. slidably engaging o site edges of the flanges |22 are shiftable cam engaging elements |22 that are in the nature of laterally' spaced pairs of shoes. 'I'he edges of the flanges ing shoes |22 are provided with undercut cross sectionally bevelled slots |24 that receive and slidably interlock with the bevelled edges of the arcuate flanges |22. These co-operating pairs of cam engaging shoes |22 are maintained in transversely aligned relation on opposite edges ofthe flanges |22 by means of operating yokes |25,

which are provided at their end's with axially aligned pivot pins |22 that work in bearing apertures formed in hubs |21 of the shiftable v cam engaging shoes. The bifurcat'ed ends of the rectionally with respect to straight lines radial of the axis of their respective cams.

In accordance with the instant example, the

surfaces |22 are disposed at a 90 angle with repointer |24 for co-operation-,with the'calibratedspect to the line :t (see line y Fig. 35)',` and the surfaces 2| are Ydisposed at a 20 angle with re,-

spect to their co-operating surfaces |20 (see line z in Fig. 35).

'I'he tappet heads |25 beingrigidly mounted on or formed with the straight line guide reciprocating tappet stems |24 constitute the non-shiftable'cam engaging elements of the tappets, and are integrally formed with arcuate flanges |22 that proiectlaterally beyond opposite sides of ofthe crank vcase with a removable yokes |25 are preferably normally spaced apart a distance slightly less than the distance between the faces lof the Ihubs ating shoes |22 so that site shoes |21 of each they will maintain oppo. pair snugly interlocked with the bevelled edges of the flanges |22. The shoes |22 have parallel cam engaging `surfaces thatjare adapted to'co-act with the liftingsurfaces of the main cam sections, it being understoodv that the opposed faces of the shoes -of each pair work closely against the opposite sides of the rigid cam heads sufficiently that they will freely receive the supplemental cam sections |22.

, The main cam section engaging surfaces |22 of the shoes |22 are ila't and straight from-end to end and in length are approximately equal to the combined length of the oblique cam engaging surfaces |22 and |2|. and are so proportioned that they will .come flush with either of the surfaces |20 or Y alignment. VPreferably in' accordance with the instant illustration, 'flanges |22 and their co.operating shoe grooves are co-incidentalwith the cam axis when the parts are positioned as shown for example in Figs. 23 and 25. Hence, in the preferred arrangement illustrated, not only have the arcuate guide surfaces |22 of the rigid tappet head |25 a radii equal to the distance therebetween and the axis of theA cam shaft when the shiftable cam engaging elements are riding on the heel of the cam. but it will be further evident thatthe locus of the axis of these guide surfaces will travel in a straight line radial of the cam axis. v

For operatively adjustably positioning and maintaining the desired relatlve'positions of the Y shoes |22 of the intake and exhaust valve operatingytappet mechanisms. there is provided, Ain addition to the yokes |25,v a control shaft |22 carrying` eccentrics |40 for. the intake valve mechanism and |4| for the exhaust valve mechanism and lever acting yokes |42. The control shaft |22 may be assumed to be suitably journaled in the crank case structure and to work -through one end thereof. Provided outward of the crank case the control |22 is equipped with an operating or control lever |42 that ,carries a segmental dial |45. The control shaft |22. the eccentrics |42 and |4| and yokes|25 an |42 are made readily accessible by providing the yside section |42. 'The yokes 42closely embrace the eccentrics v|42 and `|4| and are each pivotally mounted on a stationary shaft |41, which shaft may be assumed to be rigidly supported fromthe crank case. The

single ends of the yokes |25 are pivotally anchored in bifurcated portionsof the eccentric engaging-yokes |42 by means of pins |42. In ac- |22 are bevelled and the cam engag |21 of opposite co-oper- |25 and are spaced apart |2| with which they are pivoted intov the axis of the, arcuate guide' pins |36.

The tappet mechanism for the intake and exhaust valves are structurally alike and are rotav tively positioned alike on the axis of their respective stems |24, and also the yokes |35 and |42 are substantially alike for both the intake and exhaust valves, but the eccentrics |40 and |4| are positioned on the control 180 apart on the control shaft so that when the cam engaging surface |38 of the shoes |33 of the intake valve mechanism are aligned with the surface |30 of the intake valve tappet head, the cam engaging surfaces of the shoes of the exhaust valve mechanism will be aligned with the cam engaging surface |3| of the exhaust valve tappet head and reversely, it being understood that these represent the extremes of adjustment. Of course, the shoes`of the exhaust valve and intake valve operating tappets will be positioned substantially alike when the control shaft |39 is rotatively positioned half-way betweenjts two vextreme positions. The relative positions of the eccentrics |40 and |4| is diagrammatically'illustrated in Fig. 37;

In Figs. 22 to 40 the only means illustrated for operatingl the control shaft |39 is the lever |43 which may be assumed to be subject to manualcontrol. However, it should be understood that the control shaft may,if desired, be automatically controlled in proper relation to variations in engine speed, and this may be accomplished by means of the governor mechanism of Figs. 6, 7 and 8.

Certain of the valve timings obtainable with the described embodiment of the form of the invention illustrated'in Figs. 22 to 40 inclusive are indicated diagrammatically in Figs. 38, 39 and 40. In these gures the circles marked a' indicate onercomplete revolution or 360 `of movement of the engines crank shaft; the vertical lines marked b indicate the top dead-center position of the engines piston operating crank;'

vertical lines marked 'c' indicate bottom deadcenter position of the engines piston .operating crank; arrows d' indicate the direction of rotation of the crank shaft; lines e indicate the times of opening of the exhaust valve with respect to crank shaft position under different degrees of valve timing adjustment; lines f indicate the times of closing of the intake valves with respect to crank shaft position under different degrees of valve timing adjustment; lines g' indicate the times `of opening of the intake valve with respect to crank shaft position under diierent degrees of valve timing adjustment, and lines h' indicate the times of closing of the ining adjustment.

Operation.

For low speed engineoperation, the control shaft |39 will be rotatively positioned as indicated in Figs. 22, 22a, 23 and 24 in which position the indicator or pointer |44 of operating lever |43 will be positioned opposite the dial calibration marked low speed (see Fig. 22). With the control shaft thus positioned, the shiftable cam engaging elements or shoes |33 of the intake valve operating tappets will be posi- 'tioned as indicated in Figs. 22 and 23, and the take valve under different degrees of valve timshiftable cam engaging elements or shoes ofl the exhaust valve operating tappets |2| will be positioned as indicated in Figs.j22a and 25.

For this position of `the parts for low speed engine operation, the timing of the intake and ex -haust valves with respect to crank shaft position will be as indicated in Fig. 38. By reference to Fig's. 22 and` 23 (particularly Fig. 22) it will be seen that when the parts are thus positioned to obtain the low speed valve timing indicated in Fig.- y38, the cam engaging surfaces ofthe shoes |33 of the intake valve mechanism are aligned with the cam engaging surface '|30 of the rigid head of the tappet |20 so that the intake valve tappet |20 will be both lifted to valve open position and droppedfto valve closed position by cooperation with the liftingsurfaces of the main section of cam |22. When the parts are thus positioned, the intake valve will be opened by engagement of theleading surfaces of the main section of the intake valve operatingcarn ||8 with the horizontally disposed cam engaging surfaces of the co-operating tappet shoes |33, and

will be closed under engagement of the trailing surfaces of the cam ||8 with the surfaces |38 of the co-operating shoes |33. The supplemental cam section |23 of cam I I8 is entirely inoperative section-'|23 of the intake valve mechanism will clear its co-acting surface |3|by a full 10.

By reference now to Fig. 25, it will be seen that i with the parts positioned for low speed operation, the tappet shoes of the exhaust valve operating mechanism are advanced to a position wherein their cam engaging surfaces are. aligned with the cam' engaging surface |3| of the exhaust valve tappet |2|.

In Fig. 25 the cam is shown by dotted lines at the left in a position ready to impart initial valve opening movements to thetappet |2I, 'and the cam is illustrated by full lines at the right in the position of final exhaust valve closing.

By examination of Figs. 5, it will be evident that for extreme lower speed operation the valve operating tappet |2| will b e lifted to valve open position by engagement of the main tappet section |22 with the co-acting oblique surface |3|,

non-adjustable surface |30, while the supple-A mental cam section is only 10 rotatively'oi-set with the parts'positioned as described for extreme low speed operation, the timing of the intake and exhaust valves with respect to the cycle of the crank shaft will be as indicated in Fig. 38, and the supplemental cam sections will be entirely ineffective.

For extreme high speed operation, the control shaft |39vis rotated through the medium of the operating lever |43 in a clockwise direction in respect to the drawings until the pointer I is opposite the graduation on dial ill. marked high speed, at which time the several adjustable parts oi' the exhaust valve operating tappets III and the' control mechanism therefore will be positioned as illustrated best in Figs. 22a, 24 and 26 and the. resultanttimes of opening and closing of the intake and exhaust valves with respect to valve operating ca'm. With the parts thus posi-- tioned. the intake' valve operating tappet |20 will be raised to valve open position by engagement of the supplemental cam section III of cam III with the oblique surface ill of taDpet 120, and

said tappet 120 will be lowered to valve closed position under engagement of the trailing surface of the main cam section i2! with the projected surfaces |38 of shoes |33, which latter are now aligned with the oblique surface lll. Now.

by comparing Figs. 23 and 24. it will be evident that for high speed operation, the opening of the spect to the 'l5 'valves and the time of closing of the intake valves are shifted between two extremes of ad-l justmentmuch more than the times of closing of the exhaust valve and opening of the intake valve; It lwill also be apparent from an examination of the structures that the relative amount of shifting of the time of opening of the intake valves and closing of the exhaust valves with `retimes of clo'sing of the intake valves andopening of the exhaust valves, is controlled '-largely by the amount of angular olf-set of the supplemental cam section with respect to their integrally formed'main cam sections; and may be increased or decreased to a considerable exintake valve has been delayed 10 of cam shaft movement; whereas the time of closing of the intake valve has been delayed a full 20 of cam' shaft movement. In other words. for high speed.

the open period of the intake valve has been shifted or increased by 10 of cam movement in addition to having been bodily retarded with respect to the crank shaft.

By comparing Figs. 38 and 40.*it will be seen that between the low speed and high speed timing4 adjustments, the opening of the intake has blies. The form of tent by making variations in the angles of the .supplemental cam section without `times of closing of the intake valves of opening of the exhaust valves.

' An intermediate valve timing obtainable with effecting the and the time the arrangement described in connection with Figs. 22 to 40 inclusive is shown in Fig. 39. This intermediate valve timing is representative of the valve timing employed in certain standard vautomotive engines and, is in fact. representative of the vvalve timing found in 1938 Dodge automothe invention disclosed in Figs. V22 to '40 inclusive, has been built into a 1938 Dodge automobile engine wherein it has under-gone severe tests and shown a high del gree of increased efficiency at both high speed and low speed ranges over vthe sametype of engine incorporating the conventional xed timing valve operating mechanism.

been delayed a total, of 20 of crank shaft xnove-` ment, and the time of closing thereof has been retarded a total of 40 of crank shaft movement,

so that the actual increase in the valve opening period with respect to crank shaft movement from low speed to high speed adjustments is 20.

By reference now particularly to'Fig. 20. it

will be noted by the dotted positionof the cam at the left and bythe full line position of the cam shown at the right, that the exhaust valve tappet i2i is opened by engagement of the now horizontally disposed surfaces III of the shoesl |33 with the leading edge of the main cam section-r |22. and are lowered to valve closed position by engagement of the non-adjustable surface |30 with the supplemental cam section |23 of camila. v

Now by comparing Figs. 25 and 26. it will be seen that from the low speed position of the tap pet parts shown in Fig. 25 to the high speed position of the exhaust valve .tappet partsshown in Fig. 26, the time oi' opening of the exhaust valve has beenl advanced a full 20 of cam shaft movement; whereas, the time of closing of -the` exhaust valve has been advanced 10 of cam shaft movement.

-`shaft thus The intermediate standard timingindcated in Ilig.` 39 is brought about by setting the control shaft half-way between the extreme positions, or in-other words, in a position wherein the pointer i (see Fig. 2) is in alignment with the word Standard" onthe diall |45. With the control positioned, the shiftable cam engaging elements or shoes of the intake and exhaust valve operating mechanisms will be positioned alike with their cam engaging surfaces |38 disposed at 'a 10 angle with respect toltheir cooperating surfaces |30. and also at a 10 with respect to their co-operating surfaces |3I. It isat this midway adjusted position of the tappet shoes that the opening of the intake valves and the closing of the exhaust valves is transferred from themain cam sections to the supplemental cam sections. Hence, the entire amount of shifting ofthe time f opening of the intake valve andthe time of closing of the exhaust valve betweenextreme low speed and high speed valve first half of the adjusting range from low speed toward high speed V'during the, time .the intake valve is opened and the exhaust valve is closed By comparingA Figs. `38landf40, it will be that this valve timing variation translated into degrees oi crank shaft movement represents from low speed timing to .high speed timing an advance of $0? oi' crank shaft movement inthe opening of the exhaust valve-and an advance of 20 in the time of'closing' in the exhaust valve. the total valve open period now being 20 more.

'by engagement of theA main cam section with the surfaces 130 of theshoes i33but after-.the supplement cam' sections come into operative engagement with the non-shiftable oblique surfaces Iii at this intermediate pointi further adjustment '170' of the ,shoes i in the direction of high speed timing has no effect upon the time of opening of the intakev alve or, the time of closing of the exhaust valve, but continues to be effective in vary ing thetime of closing of the intake valve and the time of opening of the exhaust valve.

angle l Description of Fig. 12

\ arcuate guides for the shiftable tappet elements,

which arcuate guides are rigidwith the straight line guiding tappetbodies. have their-axes coaxial with the cam shaft when the tappet engag.

ing elements are riding -upon the heel of their cam in their lowered valve closed positions so that 9 under extreme high speed timing adjustment, this can be done quite successfully -by shiftlngthe axis vare indicated by Ra. With the roller 59 nowl the locus of the axis of the arcuate guide surfaces will be a straight line radial of the cam axis. While this isl considered the preferred practice in most' instances, it is the purpose of the present example to illustrate how, particularly in certain forms of the invention, this practice can be varied slightly to advantage.

The example given in Fig. 21 is based upon the structure of Figs. 1 to 22, and 20. With reference to the diagrammatic view of Fig. 2l, the cam shaft of Figs. l to 11 inclusive, is diagrammatically indicated and identified by 41 as in Figs. 1 to 11. One of the cams, as in Figs. 1 to 11, is indicated by 48, the non-shiftable tappet engaging roller is indicated by 59 and theshiftable cam engaging roller is indicated by 59. ,Also in Fig. 2l the arcuate guide slot for the shiftable roller 59 is diagrammatically indicated by broken arcuate lines 92. Rollers 58 and 59 are illustrated only in their-extreme relative shifted positions.

The circle traversed by the toe end of the cam 49 is indicated by broken line circle |49 of Fig. 21.

The axis point of the roller 58 is indicated by 6|),

and the axis point of the roller 59 is indicated by 6|. In accordance With Figs. 1 to 11, the axis of the arcuate guide 92 is co-incidental with the axis of the cam shaft when the rollers arel in their lowered positions indicated in Fig. 21. This lower co-incidental axis point is indicated by |59 in Fig. 21. Of course, this axis point moves in a straight line when the rollers are moved from their lower positions of Fig. 21 to their upper positions of Fig. 21, and this raised axis point of the arcuate guide 62 is indicated by |5011. The lower and upper arrows identified by R indicates the radius of'the arcuate guide 62 in both its lower and upper positions. It will be noted by examinving Fig. 21-that the lower arcuate guide line 62 is concentric with the cam shaft and the arcuate broken line |49, but that the upper arcuate guide f line 52 is considerably eccentric to the cam shaft, this being, of course. due to the fact that the radius R of the arc $2 has been shifted upwardly;

whereas theoretical perfection could only be obtained by increasing the radius of the arc in an amount equal to the shift. This shifting of the arc produces a very slight error in valve lift between high speed and low speed timing adjustvment of the roller 59, as will be apparent from Fig. 21 wherein it will be noted that the rollers 58 and 59 indicated by full and broken lines,` reshifted to its extreme position on the arc 92a, it will assume upperand lower positions indicated by dotted circles 59a.\

By reference to Fig. 21, it will be seen that this dotted circle 59a, in its upper position, is'

tangential with the broken line arc |49 :lust as is upper position roller 59, so that there will be no difference in valve lift between the two extremes of adjustment of the shiftable roller. However, by reference to the lower dotted circle 59a. of Fig. 21, it will be noted that in its lower extreme shifted position, the roller will now be considerably spaced from the heel of the cam. The

locus of the axis of the dotted line arcuate guide surface 62a is indicated by |52a. Obviously with the arrangement last described. the locus of the axis of the arcuate guide surface 92a is a straight line parallel to but spaced `from a line radial of the 'cam axis. This shifting of the axis point of the arcuate guide surface from point to |50' represents quite shifting is tobe done it is believed better to compromise the extent of shift toa point about half-way between points |59 and |50' as is indicated by point |50a. When this is done the arcuate guide surfaces will assume upper and lower positions asindicated by full lines 62a", the radius of thei arcs 62a' will be as indicated by arrows Rb. The roller 59 in its extreme shifted condition will assume upper and lower positions as indicated by full line circle 59a'f.

With this compromise arrangement, the shiftv able roller 59a' (see full line circles) will produce an error in valve lifting approximately half as great as when the axis of the arcuate guide is at point |50, and in its lower position, the roller 59 (see circle 59a') will be spaced only about onehalf as far from the heel of the cam as when the y axis of the arcuate guide was shifted to the exrespect to the arcuate guide surfaces for the shiftable cam engagingelements.

spectively, are both seated on the heel of the cam in their lowered positions; whereas in their upper positions, the broken line roller 59 drops considerably below the arc |49, which means that, under rotation of the cam, there will be an error in valve lift under this extreme adjustment equal to Athe distance between broken line roller 59 and broken line |49 at point |51. The locus'of the axis of the arcuate guide 52 is indicated by vertical broken line |52, which is a straight line radial of the cam axis.

Now if it is deemed desirable to substantially 'fully correct the above -noted error in valve lift (a) The axis of each of the shiftable cam engaging elements describes under reciprocation or has as the locus of its axis a straight line thatiis uni-directional with respect to a straight line radial of the cam axis. (b) The divergence of each arcuate guide surface in respect to. any straight line will be constant;l since in all forms vthe guide surfaces are positively held against tipping action during reciprocation. (c) Angular disposition of a straight line drawn between any twospaced points about any one of the arcuate guide surfaces will be constant with respect to any other straight line since in all forms of the inventionthe guide surfaces are positively held against tilting or tipping movements.

This application is a continuation in part of my tto-pending application S.' N. '753,357,21ed

an extreme shift, and if such November 16, 1934, under title Internal combustion engine.

What I claim is:

1. In an engine, a valve, a valve-actuating cam and valve actuating connections between the valve and cam, said valve actuating connections comprising a reciprocating member guided for straight line reciprocating movements and rigidly carrying a non-adjustable cam-engaging portion having a relatively flat cam engaging surface, arcuate guide means also rigidly carried by said straight line guided member, an adjustable cam engaging element having a relatively flat camengaging surface, guide means on said adjustable.element in sliding engagement with said arcuate guide means, and means for adJustably shifting said 'element about said arcuate guide surface, the axis of said arcuate guide surface being on and moving in a straight line radial of the cam axis, said cam being formed with a relatively sharp nose providing a reduced area for contact with said relatively fiat cam engaging surface whereby the period of time during whichsaid valve may be held open is materially reduced lwhen said cam engaging elements are in axial alignment.

2. In an engine, a valve, a. valve actuating cam having main and supplemental lifting surfaces that are laterally and circumferentially offset, and valve actuating connections between the cam andl valve including the reciprocating tappet body, means guiding the tappet body for true straight line reciprocating movements, a cam engaging head rigidly carried by the straight line guided tappet body and having relatively flat oblique cam engaging surfaces, and an adjustably shiftable cam engaging element carried by the rigid head of the straight line guided body A through means including an arcuate guide surface that is rigid with respect to the straight line guided tappet body, said shiftable cam engaging element having a cam engaging surface that is laterally offset from the cam engaging surfaces of the straight line guided tappet body, said cam being formedl with a relatively sharp nose providing a reduced area for contact with said relatively fiat cam engaging surface whereby the period of time during which said valve may be held open is materially reduced when said cam engaging elements are in axial alignment.

3. The structure defined in claim 2 in further combinationilwith means for adjustably shifting the said adjustable cam engaging element on the said arcuate guide surface and maintaining the same in desired adjusted position.

adapted to engage the other of the laterally offset cam surfaces, said cam being formed with a relatively sharp nose providing a reduced area for contact withi said relatively fiat cam engaging surface whereby the period of time during which said valve may be held open is materially reduced when said cam engaging elements are in axial alignment. e

5. In an engine, a valve, a valve-actuating cam and valve actuating connections between the valve and cam, said valve actuating connections comprising a reciprocating member guided for straight-line reciprocating movements and rigidly carrying a non-adjustable cam-.engaging portion having a relatively fiat cam engaging surface, arcuate guide means also said straight line guided member, an adjustable cam engaging element having a relatively flat cam-engaging surface, guide means on said adjustable element in sliding engagement with said arcuate guide means, and means for adiustably shifting said element about said arcuate guide surface, the axis of said arcuate guide surface being on and moving in a straight line that is uni-directional with respect to a straight line radial of the cam axis, said cam being formed with a relatively sharp nose providing a reduced area for contact with said relatively fiat cam en- 4. In an engine, a valve, a valve actuating cam,

oblique relatively flat cam engaging surfaces that are aligned with only one of the laterally spaced cam surfaces, arcuate guide means rigidly carried by the straight line guided tappet body for and only for straight line reciprocating movements therewith, and a cam engaging shoe slidably carried by the said arcuate guide means and having a straight cam engaging surface laterally spaced from the"cam engaging surfaces of they straight line guided 'tappet body and being gaging surface whereby the period of time during which said valve may'be held open is materially reduced when saidcam engaging elements are in axial alignment.

6. In an engine, a valve, a valve actuating cam having main and supplemental lifting surfaces that are laterally and circumferentially offset, and valve actuating connections between n the cam and valve which include a reciprocating tappet body, means guiding the tappet body for true straight line reciprocating movements, a cam engaging head rigidly carried by the straight line guided tappet body and having relatively flat cam engaging surfaces that lie in the plane of movement of the supplementallifting surface of the cam and are `obliquely disposed one in respect to the other, and an adjustably shiftable cam engaging element carried by the rigid head of the straight line guided tappet body through means including an arcuate guide surface that is rigid with respect to the straight line guided tappet body, said shiftable cam engaging element having a cam engaging surface for co-operation with the main cam section and being laterally oii'set with respect to the supplemental cam section, said cam being formed with a relatively sharp nose providing a reduced area for contact with said relatively flat cam engaging surface whereby the period of time during which said valve may be held open is materially reduced when said cam engaging elements are in axial alignment.

guiding said reciprccable tappet body for straight Y line reciprocating movements, said reciprocable tappet body being provided with a rigid cam engaging head, and arcuate guide flanges projecting laterally outwardly of said head, a laterally spaced pair of cam engaging shoes each having an arcuate slot receiving an opposite edge of said arcuate flange, whereby the shoes will be guided for arcuate adjusting movements on said arcuate flange, and means for maintaining said rigidly carried by 

